I don't think Initialize the L{FilePath} tells the reader much that they didn't already know. More useful would be something like Convert a path string to an absolute path if necessary and initialize the L{FilePath} with the result.

Since there still are no unit tests demonstrating that unicode paths work, the docstring shouldn't say that they do.

sibbling is misspelled in the sibling docstring; also it would be better to define the behavior of the method without using the name of the method. Instead of sibling, say that the resulting path has the same directory but a different base name.

There's some trailing whitespace in the patch, we try to avoid that.

The child docstring for path isn't quite correct. The path is the base name for the new FilePath to create.

String isn't a type :) str is though.

The isabs docstring is a little suboptimal, because isabs is a trick. There is no such thing as a relative FilePath, they are all absolute.

FilePath.touch doesn't actually fail silently. If the open('a').close() fails, then either it's because the path couldn't be created, in which case the utime call will fail loudly, or because of some other problem that doesn't matter because utime will still succeed, or some problem which will also cause utime to fail, which will also be loud.

For the basename docstring, seperator is actually spelled separator

It would be excellent for the dirname docstring to be parallel to the basename docstring, since the functionality is somewhat parallel.

These are all fairly minor points. I'll correct them and apply the patch. Thanks again!